Ventilation/perfusion scan

Source: Wikipedia, the free encyclopedia.
(Redirected from
Ventilation-perfusion scintigraphy
)
Ventilation/perfusion scan
Normal pulmonary ventilation and perfusion (V/Q) scan. The nuclear medicine V/Q scan is useful in the evaluation of pulmonary embolism.
OPS-301 code3-703.2

A ventilation/perfusion lung scan, also called a V/Q lung scan, or ventilation/perfusion scintigraphy, is a type of

ventilation part of the test looks at the ability of air to reach all parts of the lungs, while the perfusion
part evaluates how well blood circulates within the lungs. As Q in physiology is the letter used to describe bloodflow the term V/Q scan emerged.

Uses

This test is most commonly done in order to check for the presence of a

radiocontrast is now more commonly used for this purpose.[3][4] The V/Q scan may be used in some circumstances where radiocontrast would be inappropriate, as in allergy to contrast agent or kidney failure.[5]

A V/Q lung scan may be performed in the case of serious lung disorders such as

lobectomy surgery.[6]

Significance of results

Ventilation-perfusion scintigraphy in a woman taking oral contraceptives and valdecoxib with a pulmonary embolism. (A) After inhalation of 20 mCi of Xenon-133 gas, scintigraphic images were obtained in the posterior projection, showing uniform ventilation to lungs.. (B) After intravenous injection of 4.1 mCi of Technetium-99m-labeled macroaggregated albumin, scintigraphic images were obtained, shown here in the posterior projection. This and other views showed decreased activity in the following regions: apical segment of right upper lobe, anterior segment of right upper lobe, superior segment of right lower lobe, posterior basal segment of right lower lobe, anteromedial basal segment of left lower lobe, and lateral basal segment of left lower lobe.
V/Q Scan Interpretation
Result Interpretation Significance
Normal No perfusion deficit Excludes pulmonary thromboembolism
Low probability Perfusion deficit with matched ventilation deficit < 20% probability of PE
Intermediate probability Perfusion deficit that corresponds to parenchymal abnormality on chest x-ray 20% - 80% probability of PE
High probability Multiple segmental perfusion deficits with normal ventilation > 80% probability of PE

Decreased uptake of the inhaled radioisotope may indicate an impaired ability to breathe, airway obstruction, or possible pneumonia.

Decreased circulation of the injected MAA indicates a problem with blood flow into or within the lungs. A localized area of decreased uptake, usually in a wedge shaped (or pie shaped) configuration with normal ventilation images (mismatched defect) suggests a pulmonary embolus or blood clot in the lungs, which leads to reduced perfusion beyond the obstruction.

Risks

Although this test uses radioactive materials, the total amount of radiation exposure is low. Typical

radiocontrast can alternatively be performed, although this can result in a greater radiation dose to the patient.[9]

Procedure

The ventilation and perfusion phases of a V/Q lung scan are performed together and may include a

chest X-ray for comparison or to look for other causes of lung disease. A defect in the perfusion images requires a mismatched ventilation defect to indicate pulmonary embolism.[8]

In the ventilation phase of the test, a gaseous radionuclides such as

technetium macro aggregated albumin (Tc99m-MAA). A gamma camera acquires the images for both phases of the study.[12] A SPECT image can also be taken following an injection of Technetium labelled MAA. SPECT is often skipped if the patient has pulmonary hypertension
.

It is also possible to perform the scan with positron emission tomography (PET) rather than conventional gamma camera scintigraphy.[13] This has been performed with Gallium-68 labelled carbon nanoparticles (Galligas) using a conventional Technegas machine for ventilation images, and with Gallium-68 labelled MAA (Ga68-MAA) for perfusion images. PET has multiple potential advantages including superior resolution, speed and quantification.[14][15]

See also

References

  1. ^ "Pulmonary ventilation/perfusion scan". University of Maryland Medical Center. Retrieved 3 January 2018.
  2. S2CID 56486118
    . Retrieved 4 July 2021.
  3. PMID 25173341
    .
  4. ^ "Managing suspected pulmonary embolism". NICE. National Institute for Health and Care Excellence. January 2015.
  5. ISBN 978-1-4051-8460-1
    . Retrieved 14 November 2010.
  6. ISBN 978-1437735536
    .
  7. PMID 22282651
    .
  8. ^
    PMID 19562336
    .
  9. PMID 18165667
    .
  10. ISBN 9781841847528
    .
  11. PMID 23218595
    .
  12. PMID 28461589
    .
  13. PMID 21908388
    .
  14. PMID 27553468
    .
  15. PMID 24396515
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=Ventilation/perfusion_scan&oldid=1203775705"